require('./main.css') 
const { toLowerCase,toUpperCase } = require('./b.js')
const a = 'Hello coco,好帅';
console.log(toLowerCase(a))
console.log(toUpperCase(a))
let oDiv = document.createElement('div');
oDiv.textContent = '严总真帅!!!'
document.body.appendChild(
    oDiv
)
module.exports = a;  // commonjs